Glossary
What is email warm up?
Email warm up is the practice of raising the number of emails a new mailbox sends a little each day, so that Gmail, Outlook and other providers learn that the sender is real. It builds reputation before you send at full volume, and lowers the chance of landing in spam.
Published by Sellinger AI. Numbers and settings checked on 19 October 2026 against the fact register. Report an error.
Why does a new mailbox need it?
A mailbox with no history that suddenly sends hundreds of emails looks like a spammer. Providers judge new senders by their pattern: volume, replies, bounces and complaints. A slow ramp with real replies gives them a pattern that looks like a person.
What does a ramp look like?
| Days | Sends per day |
|---|---|
| 1 to 3 | 5 |
| 4 to 6 | 10 |
| 7 to 9 | 20 |
| 10 to 12 | 40 |
| 13 onward | The mailbox limit |
The shape Sellinger's optional warm up follows; the limit is yours.
Does warm up replace good practice?
- No. A bad list still gets complaints.
- A mailbox with a domain that is missing authentication records still lands in spam.
- Volume above what the provider tolerates still hurts after the ramp.
How Sellinger handles it
Every connected account has daily limits that the agent cannot exceed, set per account. LinkedIn defaults are 20 invitations a day and 150 a week. Email defaults to 50 sends a day per mailbox, with an optional warm up that starts at 5 a day and doubles every 3 days up to the limit.
The Limits tab of a mailbox advises starting low and raising gradually, and sets the daily maximum and the split between new outreach, follow ups and replies. See email deliverability and the help article on email sending limits.
Common questions
How long does warm up take?
Do I need a warm up tool?
Does it work on an old mailbox?
Sources and method
Sellinger email pacing and warm up in the fact register (email_worker.py), checked 19 October 2026.
Related: Email deliverability, Cold email, Email sending limits, Blog: Google and Yahoo bulk sender rules.
